Category: Broadcast Radio

Guglielmo FM and DAB Receiver Software Updated to V0.3

Thank you to Marco Greco, author of Guglielmo for writing in and noting that v0.3 has now been released. Guglielmo is a Linux based RTL-SDR FM and DAB tuner software that supports SDRs including the RTL-SDR, Airspy, SDRplay, HackRF and LimeSDR. It is designed to be an easy to use program designed for media users, rather than hobbyist technical users. He notes:

In the last two releases I have substantially improved FM and RDS decoding and added support for MOT slides.

MOT slides allow DAB broadcasters to send JPEG or PNG images files over the DAB broadcast, and compatible receivers will display it.

A ready to use Appimage for Linux systems is availalble on the Github Releases page.

Guglielmo: Screenshot of the DAB Interface

SDRAngel Features Overview: ADS-B, APT, DVB-S, DAB+, AIS, VOR, APRS, and many more built-in apps

SDRAngel is a general purpose software defined radio program that is compatible with most SDRs including the RTL-SDR. We've posted about it several times before on the blog, however we did not realize how much progress has occurred with developing various built in plugins and decoders for it.

Thanks to Jon for writing in and sharing with us a demonstration video that the SDRAngel team have released on their YouTube channel. From the video we can see that SDRAngel now comes stock with a whole host of built in decoders and apps for various radio applications making it close to an all-in-one SDR platform. The built in applications include:

  • ADS-B Decoder: Decodes aircraft ADS-B data and plots aircraft positions on a map
  • NOAA APT Decoder: Decodes NOAA weather satellite images (in black and white only)
  • DVB-S: Decodes and plays Digital TV DVB-S and DVB-S2 video
  • AIS: Decodes marine AIS data and plots vessel positions on a map
  • VOR: Decodes VOR aircraft navigational beacons, and plots bearing lines on a map, allowing you to determine your receivers position.
  • DAB+: Decodes and plays DAB digital audio signals
  • Radio Astronomy Hydrogen Line: With an appropriate radio telescope connected to the SDR, integrates and displays the Hydrogen Line FFT with various settings, and a map of the galaxy showing where your dish is pointing. Can also control a dish rotator.
  • Radio Astronomy Solar Observations: Similar to the Hydrogen line app, allows you to make solar measurements.
  • Broadcast FM: Decoding and playback. Includes RDS decoding.
  • Noise Figure Measurements: Together with a noise source you can measure the noise figure of a SDR.
  • Airband Voice: Receive multiple Airband channels simultaneously
  • Graves Radar Tracker: For Europeans, track a satellite and watch for reflections in the spectrum from the French Graves space radar. 
  • Radio Clocks: Receive and decode accurate time from radio clocks such as MSF, DCF77, TDF and WWVB.
  • APRS: Decode APRS data, and plot APRS locations and moving APRS enabled vehicles on a map with speed plot.
  • Pagers: Decode POCSAG pagers
  • APRS/AX.25 Satellite: Decode APRS messages from the ISS and NO-84 satellites, via the built in decoder and satellite tracker.
  • Channel Analyzer: Analyze signals in the frequency and time domains
  • QSO Digital and Analog Voice: Decode digital and analog voice. Digital voice handled by the built in DSD demodulator, and includes DMR, dPMR and D-Star.
  • Beacons: Monitor propagation via amateur radio beacons, and plot them on a map.

We note that the video doesn't show the following additional features such as an analog TV decoder, the SDRAngel "ChirpChat" text mode, a FreeDV decoder and several other features.

Is the Titus II Portable Android Tablet Shortwave SDR Close to Release?

The PatronX Titus II SDR is something we've been posting about several times since 2016, but in the end it was never released and assumed to be vaporware. However, we found that the website for the Titus II SDR was updated only a few weeks ago, and pricing details have been added advertising $120 and $150 for two versions of the product. But on the new website there is no store, just an email link to contact sales for ordering information. We contacted that email two weeks ago for more information but have not received a reply back yet.

The PantronX Titus II was advertised to be a portable Android tablet based SDR that would feature a 100 kHz - 2 GHz tuning range, and software that focuses on HF digital DRM decoding, as well as DAB on VHF. Computer rendered images show the tablet housed in a portable carry enclosure with two speakers. Their new website writes:

The design of rTablet / rTab defined radio receiver started in 2014. It soon became evident that electronic products available on the market could not be modified to incorporate the advanced features requested by potential buyers. This initiated the process of the innovative design of the Titus SDR (Software Defined Radio) unit. The engineering team started with a general purpose computer unit and embedding it in a broadband radio receiver module.

All types of applications, including RF software, could be installed. For example, DRM capabilities could be added as DRM is an open source. Dream Linux app was converted to run under Android mobile operating system.

The Titus rTablet / rTab being introduced to the market, is a low cost, high performance platform with many RF and PC factory installed applications.

Key feature of rTablet / rTab is the compatibility with analog (SW, AM, FM) and digital standards (DRM, DRM+, DAB, DAB+, HD). Consequently the market of rTablet / rTab is global.

The updated website with pricing and an ordering email makes us think that it might be finally on the way, but the lack of email reply is concerning. If anyone has any further information about the rTab/Titus II please be sure to share with us in the comments!

Titus II SDR updated website
Titus II Specs

Receiving the ‘Hidden’ Broadcast FM SCA Audio Subcarrier with an RTL-SDR and SDR#

Broadcast FM channels can often contain additional subcarriers hidden within the bandwidth. A common subcarrier is Radio Data System (RDS), and this is what provides song and radio station text information to your radio.

Another less commonly seen subcarrier is the Subsidiary communications authority (SCA), which is a separate audio channel hidden within the broadcast FM signal. SCA is typically used for niche radio programs, elevator music, music for doctors offices, and niche services such as reading for the visually impaired. In the past you needed a special hardware SCA radio to receive these channels, however receiving these channels with an SDR is relatively simple. Not all broadcast FM stations will have an SCA service, but the video shown below explains how to find one.

Over on YouTube channel Double A has uploaded a video showing how to decode these SCA subcarriers using an RTL-SDR, two SDR# instances and the MPX Output plugin. The idea to to use a virtual audio cable to pipe the FM Multiplex (MPX) audio output from one instance of SDR# to another. In the second SDR# instance you can then directly tune into the SCA channel. In his video he also explores the FM MPX spectrum, showing the different components, and also how to install and use RDS Spy for decoding RDS.

Tuning an FM Audio Subcarrier (SCA) & Decoding RDS Data with RTL-SDR USB

Simple FM Radio and Airband RTL-SDR Android Applications

On the Google Play store developer Knowle Consultants have recently released a new free application called "FM Radio (RTL-SDR)". This is a simple app that allows you to use a connected or remotely networked RTL-SDR to tune into preset broadcast FM stations. People wishing to use an Android enabled head unit in their car may be interested in the app as it makes tuning into broadcast FM stations easy just like it is on a standard radio.

They also have a similar app called "Airband Radio (RTL-SDR)" which provides a similar simple interface for tuning into airband presets.

Knowles Consultants simple Android RTL-SDR FM and Airband Receiver Apps

yellowShoes: A Browser Based HD Radio / NRSC-5 User Interface

Thank you to Evuraan for writing in and sharing his new browser based HD Radio / NRSC-5 interface for the nrsc5 decoder which he has called yellowShoes.

NOTE: We have been informed by some users that yellowShoes may contain a Trojan virus. This is likely to be a false positive which is a very common problem with antivirus software falsely detecting viruses on newly released niche software via heuristics. We have removed the above link out of an abundance of caution, however if you wish to continue the yellowShoes Github is here. If you want the software, but are concerned you can check the code compile it yourself.

NOTE UPDATE: The author of the software has contacted us regarding the virus concerns and written "I wanted to write in clarify that it is indeed a false positive, please see and also - this false positive occurs when you cross compile go binaries - This is a common occurrence, especially on Windows machines. Commercial virus scanning programs are often confused by the structure of Go binaries, which they don't see as often as those compiled from other languages." 

HD Radio is a digital broadcast protocol replacement for analogue broadcast FM. It is only used in North America and is easily recognized as the two rectangular blocks on either side of a broadcast FM station signal on a spectrum analyzer/waterfall display. Together with an RTL-SDR and theori's command line nrsc5 decoder, the HD Radio signal can be decoded and listened to. Evuraan writes:

I wrote yellowShoes - an nrsc5 player which you can control from your browser. (Should work on Windows, Linux etc. Player F/E also works on Android Phones.)

Its sole dependency is that the nrsc5 binary must be available in the path.

A discussion thread on Reddit has also been created.

Screenshot of the yellowShoes browser based UI for the NRSC5 decoder.

Decoding NRSC5 HD Radio with GNU Radio and a HackRF

Thank you to "LikWidChz" for submitting his tutorial on receiving and decoding multiple NRSC5 (HD Radio) channels with the help of GNU Radio, a HackRF and the NRSC5 decoder. He writes:

I wanted a way to utilize GnuRadio for working with HD radio. There are no decoder blocks from within GnuRadio to perform this decoding without an external application. This write up is how I was able to split up some signal and supply NRSC5 what it requires to perform the decode.

My goal was to capture some slice of spectrum and "channelize it" so I can perform multiple HD radio decodes at once.

In this linked zip file we have uploaded his GRC file, and his tutorial PDF, which fully explains each GNU Radio block used, and how to use the NRCS5 decoder along with the flowgraph. He also notes that if anyone wants to get in touch with him he is idling on IRC in #gnuradio and ##rtlsdr on freenode under the nickname "LikWidChz".

Channelizing NRSC5 in GNU Radio

Guglielmo: RTL-SDR FM + DAB Tuner Software for Linux

Thank you to Marco for submitting news about the release of his Linux based RTL-SDR FM and DAB tuner software package named Guglielmo. The code is based on the Qt-dab and sdr-j-fm packages, with some bug fixes, a new GUI and new audio features implemented. Marco writes:

Guglielmo implements a simple FM and DAB receiver based on Qt and the Qt-dab and sdr-j-fm packages.

The primary reason it is being developed is there is a lack of media centre quality Open Source Software Defined Radios: most of the packages out there focus more on hobbyist features, such as signal and content monitoring, leaving out media features like a volume slider or MPRIS control.

Yes, I have blown the ribbon tweeter fuses on my maggies because my previous go to SDR DAB receiver started at full blast, and I run my media centre headless: I don't really want to scramble for a VNC session when I want to stop the music, when I could simply use KDE connect on my phone.

There is also a distinct lack of FM SDR receivers, which is disappointing, since, at least in the UK, for reasons of cost, most stations transmit at a fairly poor bitRate, if not downright in mono, and FM stations seem to still be a better proposition in terms of sound quality.

If you're interested in trying it compilation instructions are available on the GitHub, and there is also a ready to use AppImage on the GitHub releases page too. 

Guglielmo: Screenshot of the DAB Interface